The present invention relates generally to electrical power distribution networks and more particularly to a transferable feeder system that allows the transfer of loads from one substation to another substation without interrupting the flow of electrical power to the loads.
Electrical power is typically produced at centralized power production facilities and transferred at high voltages to local substations. The local substations transform the electrical power to a medium or low voltage. The electrical power is subsequently distributed through feeders to local distribution networks. In general, electrical load may be transferred between distribution feeders that are connected to the same substation.
It is more difficult, however, to switch loads between networks that receive power from different substations. Since power received by each substation may come from a different source, the electrical power at one substation may have different characteristics, such as voltage and phase angle for example, than an adjacent substation. While these differences may be small, they can be large enough to make the two networks incompatible for interconnection purposes. In general, to switch a load or a group of loads from one network to an adjacent network requires the physical disconnection of hardware from the original network and reconnection to the new network. This disconnection and reconnection requires momentary interruption of service while the change is made.
Some circumstances, such as unusually high demand for example, may warrant the effort of switching loads from one network or substation to another. This is usually accomplished in areas where over-head wires are installed and connected load is radial. It should be appreciated that this type of switching is not readily applicable where underground networks are installed.
One further issue is that such a change usually requires a momentary interruption in service. Electrical utilities have a number of metrics that are used to track performance and customer satisfaction. These metrics, which include the system average interruption frequency index (“SAIFI”), the customer average interruption duration index (“CAIDI”), and for some utilities, the momentary average interruption frequency index (“MAIFI”). SAIFI measures the average number of interruptions that a customer would experience during a time period, such as a year. CAIDI measures the duration of the interruption that a customer would experience, and is generally a few hours per year. MAIFI measures the number of power interruptions that have a duration of less than five minutes that a customer would experience during a given time period.
Some or all of these metrics are also used by government regulators to aid in determining if the electrical utility is adhering to the regulations in maintaining a durable and reliable electrical service While circumstances may make it desirable to switch loads from one network to another, the process may have detrimental impacts on the utilities metrics.
Thus, while existing electrical distribution systems are suitable for their intended purpose, there remains a need for improvements. In particular, there remains a need for improvement regarding the ability to change loads from one network or a substation to another without interrupting the flow of electrical power to the load.